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UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS Guest
2024-11-22 2:29 |
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Conference: Bucharest University Faculty of Physics 2003 Meeting
Section: Solid State Physics and Materials Science
Title:
(Ba,Sr)TiO3 Ferroelectric Ceramics for Electronic Devices.
Authors:
C.Berbecaru, D.Ghetu, H.V.Alexandru, F. Stanculescu, A.Ioachim, M.I.Toacsen, G.M.Banciu, L.Nedelcu, G.Stoica
Affiliation:
Faculty of Physics, Univ.of Bucharest
Nat.Inst.Mater.Physics, Bucharest.
E-mail
Keywords:
Abstract:
Ferroelectric ceramics have important applications in microwave domain (mobile phone communications, sterable antenna, military devices, etc). BaO-SrO-TiO2 ternary compounds (BST for short), in paraelectric phase, have considerably high dielectric constant (50„i80), which can be monitored with a bias field. Temperature stability of parts per million are required for permitivity of such ferroelectric ceramics, in the usual temperature range. (Ba,Sr)TiO3 compounds were prepared by solid-state reaction. 1 mol % TiO2 rich phase composition improves the sintering and thermal treatment. The mixing-milling acetone versus distilled water media gave better results after sinterization at 1260 oC. Large temperature interval (- 196 + 150 oC) was tested in order to characterize permitivity and losses, to discern the nature and peculiar features of ferroelectric transitions. X ray structural data, collected with a Seifert diffractometer, mean size of the crystallites, samples density and porosity were measured. Permitivity and losses were measured versus temperature at 1 kHz and computer assisted microwave characteristic in 0.1„i18 GHz frequency band were obtained by Haki-Coleman method using a Courteney test fixture.
The Curie point of the transition has a linear dependence on X strontium fraction: TC(oC) „l 120 - 360„ªX. A distribution of the Curie point, typical for ceramic materials, was noticed. Dielectric losses of 10-3 at 1„i3 GHz shows Ba0.5Sr0.5TiO3 ceramic is suitable for high frequency device applications.
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